It used to be that Silicon Valley executives mainly lobbed verbal grenades toward Redmond, Wash., home of Microsoft and Bill Gates.

Now, increasingly, they are also trading fire with Texas rival Dell and its billionaire founder Michael Dell.

On Thursday, Hewlett-Packard Chief Executive Carly Fiorina tossed several jabs at the rival computer-maker while giving a speech at Oracle's annual OracleWorld trade show in San Francisco.

Without ever mentioning the company or its famous top executive by name, Fiorina derided the Texas firm for its limited spending on research and development. Hewlett-Packard of Palo Alto spends about 5 percent of its budget on R&D, compared with less than 2 percent for Dell.

"Who said R&D is overrated?" Fiorina asked. When it comes to new advances, like grid computing -- a buzzword for spreading out computing tasks among multiple machines -- Fiorina declared: "You have to be a real technology company."

The speech came just days after Sun Microsystems Chief Executive Scott McNealy took a similar swipe at Dell.

"Michael Dell is the greatest spare-parts distributor out there," McNealy said in a Tuesday interview with The Chronicle.

"He'll get you a piston ring or a carburetor or a crank shaft at really low cost. But by the way, I can buy a very low-cost automobile by buying all the parts and not paying for the assembly, labor, certification and testing," said McNealy.

Dell fired his own missiles at Sun and Silicon Valley on Monday, when he spoke at OracleWorld. He said some of the firms, which have been hit hard by the sagging economy, may never recover because they focus on proprietary technology.

Moreover, Dell denied that his company ignores R&D. Rather, the company insists that it keeps its costs down by collaborating with other firms, such as Intel and Microsoft, which have their own large development budgets. "We are not reinventing what other companies are doing," said Dell spokeswoman Deborah McNair.

Fiorina also alluded to Michael Dell's keynote speech earlier in the week, when Dell hobbled onto the stage with crutches. Dell said he hurt his ankle horseback riding.

Referring to both Dell's injury and his pledge to support grid computing, Fiorina quipped: "Some people are trying to ride this horse before the horse is ready. . . . That's a good way to hurt your foot." Grid computing -- the concept of pooling the power of small servers to minimize the cost of data centers -- was the theme of OracleWorld this year; it's a topic that Oracle Chairman and CEO Larry Ellison has pushed extensively.

Though Fiorina touted the potential for the grid concept to do for computing what the Web did for sharing documents, she also noted that there are a number of hurdles to overcome, ranging from security to overly complex software. Fiorina suggested it will take firms like HP, with significant research investments, to make the technology suitable for everyday business uses.

By contrast, Fiorina dismissed Dell and other low-cost rivals as offering little more than racks of low-end servers clustered together. "A nice rack will only get you so far," she said, drawing chuckles from the largely male audience.

But Dell dismissed the criticism, alluding to the fact that it recently overtook rivals like HP in PC sales.